Abstract:As one of the technical solutions for ultra-low-energy buildings, energy pile technology has been attracting growing attention from engineering professionals. To address the heating/cooling demands of ultra-low-energy buildings, a demonstration green building at the pilot site of "BeSTDR Infrastructure Hospital" was used as an example. Using Revit software, models were established for ultra-low-energy buildings integrated with ground-source heat pump systems with pile foundation (energy piles) and borehole buried pipes. Combined with TRNSYS software, the annual load demands of ultra-low-energy office buildings in Pingyu, Henan Province were analyzed. A comparative study was then conducted on the supply-side performance between ground-source and air-source heat pump systems. The temperature differences between supply and return water on both the source and load sides were investigated, aiming to explore the variation patterns of soil layers during the operation and maintenance of ground-source heat pump systems. Moreover, a preliminary feasibility analysis of replacing some borehole buried pipes with energy piles was conducted. The results showed that ground-source heat pump systems composed of pile foundation and borehole buried pipes achieved an energy-saving rate of over 30% compared to the air-source heat pump systems. After a cooling or heating season, the soil layer temperature of the buried pipe systems increased by 1.84℃ or decreased by 1.40℃ , respectively. After the system was in operation for 10 years, the average temperature of the soil layer of the energy pile rose to 17.40℃, and the average temperature of the soil layer of the underground pipe rose to 18.00℃ , resulting in "thermal accumulation" in the soil layer. Therefore, under engineering conditions, replacing some borehole buried pipes with pile foundation buried pipes can reduce the initial investment cost by approximately 25%, while achieving over 30% energy-saving rate in system operation.
